This invention relates to utility meters and, more particularly, to a display unit for reproducing the reading of such a meter at a location remote from the meter.
Electric, gas and water meters have to be read to determine the charges for the amount of product which has been consumed. The interval between readings may be hours, days, or months and represents, to the utility, product delivered to the consumer on credit. When the meter is not read at the specified time interval, this results in increased accounts receivable to the utility, which means lowered profit margins. It has been found that a difficult to read meter can result in additional administration expense equal to five to ten times the cost of routine meter reading. Thus, the inability to read a meter can be a major and costly problem to the utility.
Many meters are inaccessable to the utility's meter reader either on a random or continuous basis. While electric meters are almost universally mounted outside a dwelling or building, actual accessability may be limited due to such impediments as a fence, a vicious dog or being in a hazardous area. Gas meters were always mounted indoors until the advent of corrosion resistant and temperature compensated meters allowed exterior mounting. Even in such case, there still may be an accessability problem like electric meters. Water meters are almost always mounted indoors where there is even the slightest chance of freezing. Indoor meters almost always result in, at best, infrequent inaccessability.
Indoor meter inaccessability is a rapidly increasing phenomenon. Due to increasing crime rates, access to a dwelling or building is more frequently limited. Due to working families, the dwelling may be locked up. Due to increased mobility, there may not be anyone home. Consequently, utilities, especially gas and water utilities, have resorted to the major expense of relocating the meter to an accessable location outside or behind a window or have installed remote meter reading devices.
A remote meter reading device is a device mounted on the meter, generally connected to the index, which is further connected in some manner to an accessable display which reproduces the meter reading. Such remote meter reading devices vary considerably in design but generally fall into one of three types:
1. Direct Mechanical Link
The most common version of this type of remote reading device is a speedometer cable connected to the meter index on one end and a duplicate index in an accessable location on the other end. While simple and relatively low in cost, such a device is difficult to install, very limited in distance between meter and display (only several feet), is prone to mechanical failure, imposes significant and variable load on the meter which may significantly alter accuracy, and setting the remote unit numbers to correspond to the meter index is difficult.
2. Pulser
This commonly used type of remote meter reading device consists of a spring mechanically wound by the meter over a period of time and then released to obtain a high rotational velocity for a connected alternator whose resultant electrical "pulse" is transmitted over an electrical conducter to a remote accessable reading device having a solenoid activated mechanical counter. The advantage of this type of device is ease of installation, minimal effect on meter accuracy, considerable freedom on location of the accessable display (up to 200 feet is typical) and moderate cost. Disadvantages are lack of application to various meter manufacturers, difficulty in setting remote unit numbers to correspond to the meter index, a low data rate due to the winding period so that it is difficult to determine whether the meter or the remote device is working since the output is generally a ratio of 1/100 the meter output, and susceptibility to failure or missed pulses. In some cases, missing pulses may actually be a case of intentional disconnection by the customer for product theft.
3. Digital Encoder
An older version of remote meter reading devices consists of multi-contact switches connected to generally four of the index pointers (10 contacts per 4 pointers plus a common ground results in 41 output wires). These wires are connected to the remote device at an accessable location wherein each of the wires, except the common ground, is interrogated to determine the locations of the meter's index pointers. While this arrangement avoids the problem associated with pulsers and has no effect on meter accuracy, it is unreliable due to, for example, switch contact corrosion. Further, it is limited to pointer type indexes, it lacks application to various meter manufacturers, it has a low data rate since the selected pointers are the most significant digits, and the cost of installation with 41 wires can be significant. To avoid installing 41 wires, additional hardware would be required to encode the 40 possible positions to an electronic serial pulse train usable over two wires. Such a device would require expensive installation of line power to the meter.
Accordingly, it is a primary object of this invention to provide an improved arrangement for displaying the reading of a meter at a location remote from the meter.
It is a further object of this invention to provide such an arrangement which is easily adaptable to any kind of meter without regard to size or manufacturer.
It is another object of this invention to provide such an arrangement which imposes no load on the meter that might cause inaccuracy.
It is a further object of this invention to provide such an arrangement which requires no connection to line power, telephone lines, etc.
It is still another object of this invention to provide such an arrangement wherein there is great flexibility in locating the remote display unit.
It is yet another object of this invention to provide such an arrangement which requires no more than three wires between the meter and the remote display unit.
It is another object of this invention to provide such an arrangement wherein the remote display unit is easily settable to the meter index reading.
It is still a further object of this invention to provide such an arrangement having a significant data rate to indicate meter operation.
It is yet a further object of this invention to provide such an arrangement which is highly reliable and accurate in transmitting the meter reading.
It is a further object of this invention to provide such an arrangement which provides an indication of product theft.
It is yet another object of this invention to provide such an arrangement which is low in initial and maintenance costs.
It is a further object of this invention to provide an arrangement which is readable by the meter reader without the requirement for activation or special tools or devices to accept data.
It is yet another object of this invention to provide such an arrangement which operates in all environments of temperature and weather.
It is a further object of this invention to provide such an arrangement which prevents tampering with the meter or the remote display unit.